In the case of pure hyperon-mixed matter, the problem originating from such dramatic softening of the EOS has been called “hyperon puzzle”.
To resolve the hyperon puzzle, the necessity of introducing the universal three-baryon repulsion (UTBR) among hyperons and nucleons (\(YYY\) , \(YYN\) , \(YNN\) ) as well as three-nucleon (\(NNN\) ) force was pointed out [1]}.
Subsequently there appeared several works taking into account three-body and multi-body forces between baryons such as multi-pomeron exchange potential [2]}, [3]} and
\(B\) -meson (\(M\) )\(M\) , \(MMM\)  type diagrams in the relativistic mean-field (RMF) models [4]}.
Recently, theoretical approaches in the chiral effective field theory have been applied for the \(YNN\) 
interaction [5]}, [6]}.
